matlab says the inline function will be removed in future release how should i execute a string function like '2*x.^2+5'

function

[Stephen23]

When you read the inline documentation the very first line of text says:

inline will be removed in a future release. Use Anonymous Functions instead.

How about using anonymous functions, just like the documentation recommends?

Answer 1

[Star Strider]

Use Anonymous Functions (link).

Your function becomes:

fcn = @(x) 2*x.^2+5;

the call it as you would any other function:

y = fcn(x);

To convert a string to a function, use the str2func (link) function:

str = '2*x.^2+5';
fun = str2func(['@(x) ',str]);
y = fun(x);

This creates the anonymous function from the string, and returns a function handle.

[omid]

Thank you so much Sir

[omid]

Sorry I have another question If my string be different in variable for every equation and I have to use a handle for variable for example k=char(symvar(2*y^2+3) then i want to use your solution, it give me an error f=str2func(['@(k)','2*y^2+3') Is there way to use handle for variable?

[Stephen23]

Aaahh, the old X-Y problem again. See Andrei Bobrov's answer for the correct way to handle this.

[Star Strider]

@omid — My pleasure.

If you are using symbolic variables and functions, use the Symbolic Math Toolbox matlabFunction function.

[Steven Lord]

Use the symvar function to identify the variable(s) and use the char vector it returns in defining the char vector you pass into str2func.

[Alfonso Rodriguez]

Thanks for these comments. They are very useful for computational math.

Answer 2

[Andrei Bobrov]

syms y

f = matlabFunction(2*y^2+3);